The marketing of an issue of securities which effectively precedes the determination of the offer price. During the bookbuild period, the bank controlling the issue will receive firm indications from potential investors as to their level of demand at any given price so leading to the creation of a "book" of demand graded by price and quality. At the end of this period, the offer price is determined by reference to demand.

The bookbuild period may be as short as a couple of hours for a placing (an accelerated bookbuild). For further details, see Practice notes, Alternative structures for secondary issues: overview: Accelerated book build and Placings: Structure, timing and process.

For an offer involving a prospectus, the bookbuilding period commences with the publication by the company of a preliminary offering document called the pathfinder prospectus or red herring. As a guide to potential investors, the pathfinder prospectus normally contains an indicative price range within which the offer price will be set. The book will be built on the basis of this document. At the end of the period, the price is determined and the underwriting agreement entered into. The following day, the final prospectus is produced.